There are already known optical devices using colored beams enabling an aircraft in the approach phase to locate itself with respect to the approach plan, i.e. to determine if it is in the correct position, or too high, or too low, with respect to this approach plan, but these devices give information only on the positioning in elevation and do not provide any horizon reference nor azimuth reference, these latter necessitating recourse to other methods.
Furthermore, for military applications, these optical guidance devices have the obvious disadvantage of facilitating spotting by the enemy.